1. Field of the Invention
The invention relates to novel carboxy-functional organosiloxanyl derivatives and the use thereof for the treatment of the surface of leather.
2. Description of the Related Art
Leather left in the natural state is susceptible to dirt and moisture, owing to its chemical structure and its fibrous composition. As positive as its absorptivity, water absorption capacity and permeability in clothing and footwear with respect to the body's own perspiration may be, this behavior will be assessed negatively under the action of external moisture.
An important precondition for the usability of leather clothing in private and commercial use relates to its waterproof or at least substantially water-repellant properties.
In order to achieve this effect, impregnating agents based on animal, vegetable and synthetic products have already been used in the past.
Owing to their performance characteristics, the synthetic agents have very substantially become established, in particular the polysiloxanes in their various modifications.
Polysiloxanes have a high surface tension with respect to water and, owning to the greatly reduced adhesion to water, enable its cohesive forces to be fully effective, with the effect that the resulting beads and drops are repelled by the surface.
In order to increase the purely mechanical and electrostatic (van der Waals) adhesive forces of the polysiloxanes, functional groups, such as, in particular, carboxyl groups, were incorporated in the molecule. Via these groups, the polysiloxane is strongly bonded by chemical bonds to the fibers of the leather.
In comparison with the impregnating agents used therein, a substantial long-term effect could be achieved since the water-repellant protective layer is less easy to remove by scouring, abrasion or other external mechanical stresses.
EP-A-0 745 141 describes a process for waterproofing leather and skins in aqueous emulsions and in the presence of emulsifiers with polysiloxanes carboxy-functionalized in a comb-like manner, in which the carboxyl groups are bonded to the polymer main chain via spacer groups in the form of linear or branched C2–C40-alkylene groups which likewise may contain hetero atoms or hetero groups.
EP-A-0 324 345 describes a process for waterproofing leather, skins and leather substitutes, according to which polysiloxanes which preferably have terminal carboxyl groups and whose carboxyl groups are present in neutralized form are used.
WO-A-93/22464 describes a process for waterproofing leather, skins and leather substitutes using sulfosuccinic esters prepared from polyols and maleic anhydride and sulfites as water repellants, according to which alpha-/omega-OH-functional polysiloxanes can also be used as polyols.
The water repellant effect of these compounds is, however, furthermore in need of improvement with respect to water repellency, flexibility, abrasion resistance and resistance to extreme external stresses, as occur in particular in the case of work clothing or protective clothing used in industrial or military applications or the footwear used there.